Message structure

  • All transmitted data are printable ASCII characters between 20 (space) to 7E (~).
  • Data characters are all the above characters, expect the reserved characters listed below.
  • Reserved characters are:
ASCII Hex Dec Meaning
<CR> 0D 13 Carriage return
<LF> 0A 10 Line feed, end delimiter
$ 24 36 Start delimiter
* 2A 42 Checksum delimiter
; 3B 59 Field delimiter
  • The start character for each message is a $; the next two characters identify the SpringCard/SpringCore family (SC) and then the next three characters identify the type of message.
  • All data fields that follow are delimited by a semi-colon ;.
  • Fields having no data, or where data is not significant, are left empty (no character before the next delimiter).
  • The checksum is the bitwise XOR of ASCII codes of all characters between the $ and * (both delimiters are not included in the checksum). The checksum is expressed as a two-digit hexadecimal number.